1. Field of the Invention
The present invention relates to a two-stroke engine to be mounted, for example, on a lawn mower, a backpacked power sprayer, or the like and, more particularly, to a two-stroke engine achieving reduction of hydrocarbons (THC: Total Hydro Carbon: total amount of hydrocarbons) in exhaust gas.
2. Related Background Art
In a two-stroke engine mounted on a lawn mower or a backpacked power sprayer, an air-fuel mixture in a crank chamber is introduced through a scavenging port into a combustion chamber in a scavenging stroke to fill the combustion chamber while scavenging the combustion chamber. For this reason, the conventional two-stroke engines experienced so-called “blow-by”: the fresh charge gas (air-fuel mixture) introduced through the scavenging port into the combustion chamber directly blew through the exhaust port without staying in the combustion chamber. This blow-by mixture was sometimes released as unburned gas into the atmosphere without being cleaned up. In recent years, in order to reduce the blow-by of the air-fuel mixture, two-stroke engines performing so-called stratified scavenging were put into practical use (Japanese Patent Application Laid-Open No. 2001-140651 and Japanese Patent Application Laid-Open No. 2000-320338).